During the World War II, Bosnian Serbs were put under the rule of the fascistUstaša regime in the Independent State of Croatia. Under Ustaša rule Serbs along with Jews and Roma people, were subjected to systematic genocide where hundreds of thousands of civilian Serbs were murdered. According to the US Holocaust Museum, 320,000-340,000 Serbs were murdered under Ustasha rule.[4] According to Yad Vashem Holocaust Museum and Research Center,"More than 500,000 Serbs were murdered in horribly sadistic ways, 250,000 were expelled, and another 200,000 were forced to convert"[5] during WWII in the Independent State of Croatia (modern-day Croatia and Bosnia).

In 1994, the Federal Republic of Yugoslavia imposed sanctions after the National Assembly of the Serb Republic refused the Vance-Owen peace plan. In 1995, Operation Storm eliminated the Republic of the Serb Frontier. The Croatian Army continued the offensive into the Serb Republic under General Ante Gotovina. Some 250,000 Serbs fled to the Serb Republic and Serbia from Croatia, as the Serb side continued a full retreat of Serbs from the Una to the Sana river. The Croatian Army, supported by the forces of the Muslim-Croat Federation of Bosnia and Herzegovina came within 20 km of the de facto Bosnian Serb capital, Banja Luka. The war was halted with the Dayton Peace Agreement which recognized Republika Srpska, comprising 49% of the soil of BiH, as one of the two territorial entities of the Republic of Bosnia and Herzegovina. The Serb side suffered a total 30,700 victims - 16,700 civilians and 14,000 military personnel, according to the Demographic Unit at the ICTY. Although exact numbers are disputed, it is generally agreed that the Bosnian War claimed the lives of about 200,000 people - Bosniaks, Croats and Serbs. More reliable numbers place the number of deceased during the war at around 100,000-104,000 (ICTY, 2011).See: Casualties of the Bosnian War